Atomic and molecular electronic spectra and properties from the electron propagator

Decoupling in terms of the superoperator formalism according to Pickup and Goscinski is employed to find tractable forms of the self-energy operator leading to direct calculation of the electron propagator or Green's function. This is applied to the calculation of photoelectron line spectra, ground state total energies, and electronic properties of atoms and molecules. Numerical results for the helium atom and the nitrogen molecule are reported.